Two cases of melanosis of the dentate nucleus are reported. In the first patient, a child with extensive hairy nevi, both malignant melanoma and melanocytes were disseminated in the leptomeninges and central nervous system. The second case is unique. The patient did not have a melanoma, but neuromelanin was deposited in both dentate nuclei. Increased amounts of melanin precursors, derived from neurons or glia, may have been converted to neuromelanin as a result of catalysis by local concentrations of metals or enzymes. Experimentally, an oxidative process catalyzed metallically was used to “melanize” the olivary and dentate nuclei. Both neurons and parenchyma were affected. Our observations demonstrate that lipofuscin and melanin are closely related.